This invention relates to a current limiting device and a circuit interrupter having a current limiting function.
FIG. 147 is a perspective view and a partial sectional view showing a conventional circuit interrupter disclosed for example in Japanese Patent Publication No. 1-43973, in which 1130 is a current limiting element portion connected in electrically series to the interrupter portion 1140 by a conductor 1290, 1001 is a movable member of the current limiting element portion 1130 having a support member 1711 including a movable contact 1002 and a magnetic material, 1005 is a stationary member of the current limiting element portion 1130 and having a stationary contact 1006, the movable member 1001 and the stationary member 1005 together constituting a contact pair. 1280 is an excitation coil connected in electrically series to the contact pair, 1018 is a movable member contacting pressure spring for generating a suitable contacting pressure in the contact pair. 1015 is a terminal portion, 1045 is a handle, 1721 is a flexible conductor, 1095 is a spring seat, 1110 are exhaust holes, 1135 is a piston, and 1300 is a packing. FIG. 148 is a right hand side view of FIG. 147.
During the normal current supplying operation, a current flows through the circuit interrupter from the interrupter portion 1140, the conductor 1290, the excitation coil 1280, the movable member 1001, the stationary member 1005 and the terminal portion 1015. When a current of an amount with which the current limiting element portion 1130 is to achieve the current limiting operation flows, the contacts separate due to an electromagnetic repulsive force generated between the movable contact 1002 and the stationary contact 1006 and generate an electric arc. This arc increases the pressure between the contacts, so that the piston 1135 of the movable member 1001 is moved against the force of the spring 1018. Also, since one portion of the movable member 1001 is a support member 1711 made of a magnetic material, the excitation coil 1280 constituting a coil plunger also provides a force assisting the contact opening. When the movable member 1001 moves in the contact opening direction, the gas on the back side of the movable contact is exhausted through the exhaust holes 1110, whereby the pressure increased by the arc is also additionally exhausted. The contact open state is maintained until the pressure sufficient to hold the contact in the opened state against the force of the movable contact contacting pressure spring 1018 is not provided
Then, when the current flowing through the current limiting element portion decrease and the arc pressure decreased to a certain value, the movable member 1001 initiates its contact closing operation due to the force of the movable contact contacting pressure spring 1018. At this time, in order to delay the contact closing process, the exhaust holes 1110 are formed at an acute angle with respect to the contact opening direction, thereby to increase the fluid resistance of the gas to be exhausted. Also, the direction of tilt of the exhaust holes 1110 serves to reduce the fluid resistance of the gas at the time of the contact opening operation. In the current limiting element portion 1130 having such the structure, the fault current flowing through the circuit is limited mainly by an inductance of the excitation coil 1280 and the electrical resistance generated between the contacts 1002 and 1006. Since the contact pair is positioned within a narrow cylindrical space, the arc pressure generated upon the current limiting operation is increased to increase the resistivity of the arc. Therefore, a high arc voltage necessary for current limiting can be obtained. The current thus current-limited is eventually interrupted by the interrupter portion 1140 connected in series to the current limiting element portion.
FIG. 149 is a partial sectional view showing a conventional three pole current limiting unit disclosed for example in Japanese Patent Publication No. 8-8048, in which a current limiting unit 1200 constitutes a current limiting interrupter (a circuit interrupter with a current limiting function) together with a standard circuit interrupter 1300 which are connected at their housings. FIG. 151 is a partial sectional view with one portion of the housing side wall removed in order to show the internal structure of the current limiting interrupter. The current limiting unit 1200 contains in the respective inner poles two pairs of contact pairs connected in series as shown in FIG. 152. FIG. 153 is an exploded perspective view in which main parts are disassembled in order to show the structure of the two contact pairs shown in FIG. 152.
In FIGS. 148 to 153, 1a and 1b are first movable member and a second movable member constituted by the movable contacts 1002a and 1002b and the movable arms 1004a and 1004b, respectively, and 1005a and 1005b are first stationary contact and a second stationary contact constituted by the stationary contacts 1006a and 1006b and the stationary conductors 1007a and 1007b, respectively. The first movable member 1001a and the first stationary member 1005a, and the second movable member 1001b and the second stationary member 1005b constitute contact pairs, respectively. 1015a, 1015b and 1015c are terminal portions disposed at one face of the housing, 1016a, 1016b and 1016c are terminal portions disposed at the opposite face of the housing, the first stationary member 1005a being connected to the terminal portion 1016a and the second stationary member 1005b being connected to the terminal portion 1015a through the connecting conductor 1014, and the first movable member 101a and the second movable member 1001b are electrically connected by the flexible conductor 1072 to the end portion opposite to the movable contacts 1002a and 1002b. 
Therefore, the current path extends from the terminal portion 1016a, the stationary conductor 1007a, the stationary contact 1006a, the movable contact 1002a, the movable arm 1004a, the flexible conductor 1072, the movable arm 1004b, the movable contact 1002b, the stationary contact 1006b, the stationary conductor 1007b, the connecting conductor 1014 and the terminal portion 1015a, and two pairs of contact pairs are electrically connected in series. The two contact pairs are separated and arranged in plane symmetry with respect to a plane of the partition wall 1100 substantially perpendicularly disposed with respect to a plane (the bottom surface of the housing) connecting the terminal portions 1015a and 1016a disposed at the opposite ends of the housing separated. A rotary shaft 1013 penetrating through the partition wall 1100 rotatably supports the first movable member 1001a and the second movable member 1001b, and the first movable member 1001a and the second movable member 1001b are urged toward the first stationary member 1005a and the second stationary member 1005b, respectively, by means of twist springs 1011a and 1011b (not shown). At the position opposing to the tip end portion on which the contacts of the above contact pairs are provided, arc extinguishing plates 1019a and 1019b (not shown) of a horse-shoe shape are provided.
At the time of normal opening and closing as well as overload current interrupting, the standard circuit interrupter 1300 achieves opening and closing operation and the interrupting operation, and the current limiting unit 1200 does not operate. On the other hand, when a large current such as a short circuited current is generated, two contact pairs disposed within the current limiting unit 1200 is rapidly separated against the spring force of the springs 1011a and 1011b by the electromagnetic repulsive force generated by the parallel and opposite currents flowing through the stationary conductor 1007a and the movable arm 1004a as well as the stationary conductor 1007b and the movable arm 1004b, respectively. Also, the current flowing through the connecting conductor 1014 generates a magnetic field component in the direction of separating the movable members 1001a and 1001b. 
As these contact pairs rapidly separate, two point series arc generates and the arc voltage rapidly rises. By this rapid rise of the arc voltage, the short circuit current is quickly pinched and the current peak is suppressed. Each of two arcs generated across two contacts is elongated by the function of the current flowing through the stationary conductor 1007a or 1007b and the movable arm 1004a or 1004b and the connecting conductor 1014 toward the arc extinguishing plates 1019a and 1019b, where they are cooled and splitted. This causes the fault current to be further pinched, rapidly proceeding to the current zero point. By the current limiting operation of the current limiting unit 1200 as above discussed, the fault current pinched to be small is interrupted by the standard circuit interrupter 1300 connected in series with the current limiting unit 1200. After the current interruption, the movable members 1001a and 1001b returns to the closed state by the action of the springs 1011a and 1011b. 
During the above-discussed current limiting operation, the electromagnetic repulsive forces acting on the first movable member 1001a and the second movable member 1001b are substantially equal magnitude to each other because both the contact pairs are arranged in a plane-symmetrical relationship relative to the symmetry plane of the partition wall 1100, the separating speed of both contact pairs are substantially the same. Therefore, the flexible conductor 1072 connecting the first movable member 1001a and the second movable member 1001b is not subjected to a twisting force. Also, since the arc energy treated in two spaces partitioned by the partition wall 1100 is substantially equal to each other, it is cannot happen that the parts disposed within one of the spaces, such as the movable contact, the stationary contact, the arc extinguishing plates or the like are worn significantly more than the similar parts disposed in the other space.
When a current limiting interrupter is constituted by directly connecting the current limiting unit 1200 and the standard circuit interrupter 1300, the overall length of the current limiting interrupter becomes too long and deteriorates the easy housing within the distribution panel or the like when the length L of the current limiting unit 1200 is too long. Therefore, in the conventional current limiting unit, the contact pairs are arranged so that their longitudinal direction substantially perpendicularly crosses the plane connecting the terminal portions disposed at the opposite ends of the housing and that two contact pairs are positioned side by side in the width direction, thereby to minimize the increase of the length of the longitudinal direction of the current limiting interrupter. Also, taking the easy placement within the distribution panel or the like into consideration, it is apparent that the width W and the height H of the current limiting unit 1200 is equal to or less than the width and the height of the standard circuit interrupter 1300. However, if the connection between the current limiting unit 1200 and the standard circuit interrupter 1300 is considered, the width W of the current limiting unit 1200 is preferably equal to the width of the standard circuit interrupter 1300.
In the current limiting element portion of conventional the circuit interrupter as shown in FIGS. 147 and 178, the movable contacts are always positioned within a narrow space of a cylindrical shape, so that the vapor of the electrode metal filled within the space upon the arc generation prevents sufficient insulation recovery upon the current interruption. Also, the movable contacts apt to get into contact with the cylindrical wall surface, resulting in a high possibility of insulation breakdown at the wall surface. For these reasons, it is difficult for the current limiting element portion alone to obtain a current interrupting function and it is necessary to additionally provide an interruption portion having a current interrupting function. Therefore, the overall size of the circuit interrupter becomes large, the structure becomes complex and the cost becomes high.
Also, when the current limiting element portion 1130 and the interrupting portion 1140 are connected in series as previously discussed, the impedance of the entire circuit interrupter becomes large. In particular, the excitation coil 1280 is provided in the current limiting element portion 1130 for assisting the contact separation of the movable member 1001 upon the current limiting operation, thus increasing the impedance. In such the circuit interrupter of high impedance, a high current carrying loss and an abnormal temperature rise due to the current carrying may easily be generated. Therefore, when a large current carrying capacity is required, such the conventional circuit interrupter cannot be used.
Further, in the current limiting element portion 1130 of the conventional circuit interrupter, the contact opening operation of the movable member 1001 is linearly carried out, so that the dimension of the circuit interrupter in the direction of the opening and closing movement of the contact member 1001 (contact opening and closing movement) become large in order to ensure a sufficient contact separating distance. As shown in FIG. 147, the dimension in that direction is a sum of the terminal portion, the stationary member, the movable member, the space in which the movable member moves, the space in which the flexible conductor is housed and the thickness of the housing wall. Therefore, when there is a limit in the dimension in the direction of movement of the movable member, a sufficient separating distance cannot be ensured and the high pressure cannot be effectively related to the arc voltage increase.
Also, when the high pressure could not be effectively related to the arc voltage increase, unnecessary pressure rise is generated, resulting in a problem that a very high housing strength is needed for suppressing the pressure rise.
Also, in the current limiting device shown in FIGS. 149 to 153, when the current limiting unit has a limitation on its width dimension as above discussed, and with the two contact pairs are arrange side by side in the width direction in order to reduce the length dimension of the current limiting unit, the housing side wall may be difficult to have a thickness providing a sufficiently large mechanical strength. Therefore, the housing may be damaged by the internal pressure rise due to the arc generated upon the current limiting operation. Also, even when the damages of the housing is prevented by selecting a mechanically strong material, the cost of the housing will be increased.
Also, two pairs of contact member pairs are connected in series for obtaining a high current limiting performance, so that the head generated at the contact surface of the contact element during the current carrying becomes two times, the electrical path length within the current limiting unit is increased and the heat conduction to the external conductor, an abnormal temperature rise during the current carrying can easily be generated, so that this arrangement is difficult to be applied to a circuit of a large current carrying capacity.
Also, since two pairs of contact member pairs are connected in series and two arc extinguishers are provided, number of the parts is large and the cost is high.
Also, when the circuit is composed of the conventional current limiting device and the electromagnetic switch low in welding resistivity, since the contact welding may be generated due to contact floating upon the short circuit interruption, it is necessary that the electromagnetic switch be designed to have the weld resistance. Therefore, when a current limiting performance exceeding the conventional current limiting device can be realized, the welding resistance performance of the electromagnetic switch connected in series to the circuit can be lowered and the cost of the electromagnetic switch can be decreased, so that further improvements in current limiting performance are required.
The present invention has been made in order to solve the above-discussed problems and has as its object the provision of a current limiting device of low cost having an improved current limiting performance and interrupting function with a single arc extinguisher.
Another object of this invention is to provide a current limiting device high in current limiting performance and small impedance.
Another object of this invention is to provide a small current limiting device having a small dimension in the direction of the contact opening and closing operation.
Another object of this invention is to provide a current limiting device in which the increase of the housing internal pressure upon the interruption that does not effectively contribute to the improvements in current limiting performance is suppressed, whereby the required housing strength can be reduced.
Further object of the present invention is to provide a circuit interrupter of low cost having an improved current limiting performance and interrupting function with a single arc extinguisher.
Another object of this invention is to provide a circuit interrupter having a current interrupter high in current limiting performance and small impedance.
Another object of this invention is to provide a circuit interrupter having a small current limiting device having a small dimension in the direction of the contact opening and closing operation.
Another object of this invention is to provide a circuit interrupter having a current limiting device in which the increase of the housing internal pressure upon the interruption that does not effectively contribute to the improvements in current limiting performance is suppressed, whereby the required housing strength can be reduced.
Still another object of the present invention is to provide a current limiting device having a good current limiting function and in which housing cracks due to the internal pressure rise upon the current limiting operation cannot easily be generated.
Still another object of the present invention is to provide a current limiting device having a good current limiting function and in which an abnormal temperature rise upon the current carrying cannot easily be generated.
Still another object of the present invention is to provide a current limiting device having a good current limiting function and small in number of parts.
Still another object of the present invention is to provide a current limiting device in which current limiting function is further improved.
The current limiting device of the present invention comprises: a first and a second contact member having at each one end portion to define a pair of contact pairs; means for providing a contacting pressure to the contact pairs and; a cylindrical insulator cylindrically surrounding around the contacts in the closed state; at least one of the contact of the first and second contact members being rotatably supported at the other end portion; an electrical path is being defined through which currents flow in substantial opposition to said first and second contact members and in opposite direction to each other and the one end portions having contacts of the first and second contact members are positioned within the cylindrical space defined by the cylindrical insulator in the contact closed state; and the contact of at least one of the rotatably supported contact members are positioned outside of the cylindrical space defined by the cylindrical insulator in the contact opened state.
The current limiting device may comprise: a movable member having a movable contact and a movable arm and rotatable about the movable member rotary shaft; a stationary member having a stationary contact making a contact pair with the movable contact and a stationary conductor substantially opposing to the movable arm; a cylindrical insulator cylindrically surrounding around the contact pair in the closed state; and a contact pressure spring providing a contact pressure to the contact pair; the movable arm having a movable arm horizontal portion and a movable arm vertical portion defining a substantially L-shape and, in the contact closed state, the movable arm horizontal portion being positioned to provide a current flow substantially parallel to and opposite in direction with respect to the stationary conductor, and a movable member tip portion having the movable contact and a stationary member tip portion having the stationary contact being positioned within the cylindrical space defined by the cylindrical insulator and the movable contacts, and, in the contact open state, the movable contact being positioned outside of the cylindrical space.
The arrangement may be such that the conductor is bent into a substantially U-shape with one end thereof being connected to the terminal portion on the far side far from the movable member rotary shaft, and the other end of the U-shape has on its inner side a stationary contact to provide the stationary contact with respect to the movable member; one of the stationary members on which the stationary contact is disposed defining the stationary conductor substantially opposing to the movable arm horizontal portion in the closed state, the stationary member being provided with a slit for allowing the opening and closing of the movable member at the position crossing the rotary trace of the movable member; and the portion other than the stationary contact of the stationary member directly facing with the movable contact in the contact opened state is covered by the insulating material.
Also, the arrangement may be such that the stationary member made of a conductor connected to the terminal portion on the far side from the movable member rotary shaft has defined therein a stationary conductor having the stationary contact making the contact pair with the movable contact and opposing to the movable arm horizontal portion of the movable member and through which a electric current opposite to the current through the movable arm flows, and wherein a magnetic core is disposed on the electric path disposed at both sides of the stationary conductor and introducing a current to the stationary conductor from the terminal portion.
The stationary conductor may be bent so that it is closer to the movable arm horizontal portion that to the stationary contact.
The current limiting device may comprise: a movable member having a movable contact and a movable arm and rotatable about the movable member rotary shaft; a repulsive member having a repulsive contact making a contact pair with the movable contact and a repulsive arm substantially opposing to the movable arm and rotatable about a repulsive member rotary shaft; a cylindrical insulator cylindrically surrounding around the contact pair in the closed state; a contact pressure spring providing a contact pressure to the contact pair; and a pressure accumulating space communicated at its main opening portion to the cylindrical space defined by the cylindrical insulator and having the repulsive member therein; the repulsive arm having a repulsive arm horizontal portion and a repulsive arm vertical portion defining a substantially L-shape and, in the contact closed state, the repulsive arm horizontal portion being positioned to provide a current flow substantially parallel to and opposite in direction with respect to one portion of the movable arm, and a movable member tip portion having the movable contact and a repulsive member tip portion having the repulsive contact being positioned within the cylindrical space defined by cylindrical insulator and the movable contacts, and, in the contact open state, the movable contact member tip portion being positioned outside of the cylindrical space.
The arrangement may be such that an electrical path for supplying a current to the repulsive member is provided on the side remote from the movable member of the repulsive member, and a portion opposite at least to the repulsive member tip portion of the electrical path is provided with a slit having a width substantially equal to that of the repulsive member along a plane including a locus of the repulsive member in the contact opening operation.
The arrangement may be such that an electrical path for supplying a current to the repulsive member is arranged to intersect with a plane including the contact opening locus of the repulsive member, the electrical path is provided with a slit for allowing the opening and closing movement of the repulsive member or the movable member, and wherein the electrical path is positioned closer to the movable arm than to the repulsive arm horizontal portion so that an electric current parallel to and opposite to the repulsive arm horizontal portion flows.
The current limiting device may comprise: a movable member contained within an electrically insulating housing and having a movable contact and a movable arm of substantially L-shape and rotatable about the movable member rotary shaft; a stationary member having a stationary contact making a contact pair with the movable contact and a an electrical path substantially parallel to one portion of the movable arm and allowing an electric current to flow in the opposite direction to the movable arm upon contact closing; a cylindrical insulator cylindrically surrounding the contact pair in the closed state; biasing means for providing contact pressure to the contact pair; an arc extinguishing plate disposed at a position opposing to the tip of the movable member; and a terminal portion disposed on the opposite side of the insulating housing and connected to the movable member and the stationary member; the stationary member being substantially perpendicularly provided with respect to a line connecting both of the terminal portions; and, in the contact closed state, the contact pair being positioned within the cylindrical space and, in the contact open state, the movable contact being positioned outside of the cylindrical space.
The arrangement may be such that the terminal portion is disposed at a position higher than the bottom surface of the insulating housing, and the movable member and the stationary member are arranged to be connected to the terminal portion on the side far from the respective movable member and the stationary member through a bent electrical path from the mutually parallel electrical path.
The arrangement may be such that two pairs of the contact pair of the movable member and the stationary member are provided and these contact pairs are electrically connected in series and separated by a partition wall from each other.
The arrangement may be such that the height of the wall of the cylindrical insulator cylindrically surrounding the contact pair in the closed state opposite to the movable member rotary shaft is higher than the wall on the side of the movable member rotary shaft.
The arrangement may be such that the movable member, the stationary member and the cylindrical insulator cylindrically surrounding the contact pair in the closed state are housed within a housing, the housing has an exhaust port formed in the face of the housing opposite to the movable member rotary shaft as viewed from the movable contact, and wherein the exhaust port has an area equal to or less than one half of the area of the housing including the exhaust port and is positioned at a position close to the movable member in the open state.
The current limiting device may further comprise an arc extinguisher plate disposed at a position opposing to the tip of the movable member and an arc runner extending along the current supplying conductor to the stationary member, the end portion of the arc runner being exposed to the arc extinguisher plate side from the portion of the cylindrical insulator opposite to the movable member rotary shaft.
The arrangement may be such that the portion of the stationary conductor opposing to the movable member and through which an electrical current opposite to that of the movable member flows is bent so as to be close to the movable member.
The current limiting device may further comprise a commutation electrode connected to the current supplying conductor of the movable member of which tip portion reaches close to the arc extinguishing plate is disposed behind the movable member in the closed state.
The circuit interrupter having current limiting function may comprise: a movable member having a movable contact and a movable arm and rotatable about the movable member rotary shaft; a stationary member having a stationary contact making a contact pair with the movable contact and a stationary conductor substantially opposing to the movable arm; a cylindrical insulator cylindrically surrounding the contact pair in the closed state; and a contact pressure spring providing a contact pressure to the contact pair; the arrangement being such that the contact pair is positioned within a cylindrical space defined by the cylindrical insulator in the contact closed state, and the movable contact is positioned outside of the cylindrical space in the contact open state.
The arrangement may be such that the movable arm has a movable arm horizontal portion and a movable arm vertical portion defining a substantially L-shape and, in the contact closed state, the movable arm horizontal portion being positioned to provide a current flow substantially parallel to and opposite in direction with respect to the stationary conductor.
The arrangement may be such that the cylindrical insulator comprises in an inner wall surface defining the cylindrical space a shed or grooves for increasing the area that is brought into contact with the electric arc.
The arrangement may be such that the material of the cylindrical insulator defining the cylindrical space is different between the portion surrounding the contact pair and the other remaining portion, the portion surrounding the contact pair being made of a material that easily emits a large amount of vapor by the electric arc.
The arrangement may be such that the inner wall of the cylindrical space has a configuration extending along the rotation locus of the tip of the movable member.
The arrangement may be such that the stationary member positioned within the cylindrical space has an insulating material covering around the stationary contact so that the stationary contact alone is exposed to the cylindrical space.
The arrangement may be such that the height of the wall of the cylindrical insulator cylindrically surrounding the contact pair in the closed state opposite to the movable member rotary shaft is higher than the wall on the side of the movable member rotary shaft.
The arrangement may be such that the stationary conductor defining the stationary member and one portion of the conductor for supplying the current to the movable member are arranged in parallel and close to each other so that the electric currents flowing through both of the above conductors during the current conduction are coincide in the direction of current flow.
The arrangement may be such that the stationary conductor and the conductor for supplying current to the movable member are arranged in parallel to each other in a plane including the locus along which the movable member rotates.
The arrangement may be such that a magnetic core surrounding the stationary conductor and the conductor for supplying current to the movable member is provided and the magnetic core has opposite poles arranged in opposition to the movable arm horizontal portion in the contact closed state.
The arrangement may be such that a magnetic core surrounding the stationary conductor, the conductor for supplying current to the movable member and the movable member is provided.
The arrangement may be such that the movable member, the stationary member and the cylindrical insulator cylindrically surrounding the contact pair in the closed state are housed within a housing, the housing has an exhaust port formed in the face of the housing opposite to the movable member rotary shaft as viewed from the movable contact, and wherein the exhaust port has an area equal to or less than one half of the area of the housing including the exhaust port and is positioned at a position close to the movable member in the open state.
The arrangement may be such that a commutation electrode connected to the current supplying conductor to the movable member and of which tip portion reaches close to the exhaust port above the arc extinguishing plate is provided, the commutation electrode is provided with a slit for allowing the rotation of the movable member so that the movable contact is positioned close to the commutation electrode in the movable member open position.
The arrangement may be such that a magnetic core disposed to sandwich the housing from the externally above and below the housing or surrounding the housing is provided at a position along an opening locus of the movable member.
The arrangement may be such that the stationary contact is positioned within the pressure accumulating space communicated with the cylindrical space.
The arrangement may be such that one portion of the stationary conductor around the stationary contact is covered with an electrical insulation.
The arrangement may be such that the pressure accumulating space is disposed only above the stationary member.
The circuit interrupter having a current limiting function may further comprise an arc extinguisher plate disposed at a position opposing to the tip of the movable member and an arc runner extending along the current supplying conductor to the stationary member, the end portion of the arc runner being exposed to the arc extinguisher plate side from the portion of the cylindrical insulator opposite to the movable member rotary center.
The arrangement may be such that the tip portion of the arc runner is positioned lower than the upper face of the cylindrical insulator therearound.
The arrangement may be such that the cylindrical space in which the stationary contact is positioned and the arc runner cylindrical space surrounding the arc runner tip are communicated through a conduit.
The arrangement may be such that the movable arm has a hook-shaped configuration.
The arrangement may be such that the movable arm has an S-shaped configuration.
The arrangement may be such that a portion of the movable arm directly facing the stationary contact surface on the side of the movable member rotating center is covered by an insulator.
The arrangement may be such that a portion of the stationary conductor opposing to the movable arm is bent toward the movable arm to provide a portion parallel to the movable arm.
The arrangement may be such that an arc extinguishing plate disposed at a position opposing to the tip of the movable member and an opposing electrode disposed above the arc extinguisher plate in the vicinity of the end face of the movable member on the side of the arc extinguisher plate in the open position.
The arrangement may be such that an arc extinguishing plate disposed at a position opposing to the tip of the movable member is provided, and wherein the height of the inner wall of the cylindrical insulator on the side of the movable member rotary center is higher than the wall on the opposite side of the movable member rotary shaft in order that the movable member side opening portion of the cylindrical space defined by the cylindrical insulator faces toward the arc extinguishing plate.
The arrangement may be such that a plurality of horse shoe shaped arc extinguishing plate are provided, and wherein the portion of the arc extinguishing plates at the inner surface of the central portion of the horse shoe is positioned between a plate extended from the wall surface of the cylindrical insulator opposite to the movable member rotary center and a locus of the tip portion of the movable member.
The arrangement may be such that the stationary conductor having the stationary contact is bent into a substantially U-shape to lead to a far side from the movable member rotary center, and wherein a slit for allowing closing of the movable member is provided in the portion of the stationary conductor intersecting with the rotation locus of the movable member.
The arrangement may be such that the portion of the stationary conductor opposing to the movable member and in which the current direction is opposite to the movable member is bent to be close to the movable member.
The arrangement may be such that the stationary conductor directly facing to the movable contact in the open state is covered with an electric insulator.
The arrangement may be such that the stationary conductor is lead to the side far from the movable member rotary center, and wherein the arrangement is such that one portion of the stationary conductor opposes to the movable member and that the direction of electric current flowing through the opposing portion is opposite to that of the movable member.
The current limiting device may comprise: a movable member contained within an electrically insulating housing and having a movable contact and a movable arm of substantially L-shape and rotatable about the movable member rotary shaft; a stationary member having a stationary contact making a contact pair with the movable contact and a an electrical path substantially parallel to one portion of the movable arm and allowing an electric current to flow in the opposite direction to the movable arm upon contact closing; a cylindrical insulator cylindrically surrounding the contact pair in the closed state; biasing means for providing contact pressure to the contact pair; an arc extinguishing plate disposed at a position opposing to the tip of the movable member; and a terminal portion disposed on the opposite side of the insulating housing and connected to the movable member and the stationary member; the contact pair, in the contact closed state, being positioned within the cylindrical space and, in the contact open state, the movable contact being positioned outside of the cylindrical space.
The arrangement may be such that the terminal portion is disposed at a position higher than the bottom surface of the insulating housing.
The arrangement may be such that the movable member and the stationary member are connected to the terminal portion closer to the movable member and the stationary member through an electrical path bent into a xe2x80x9cU-shapexe2x80x9d from an electrical path parallel to each other.
The arrangement may be such that the movable member and the stationary member are connected to the terminal portion farther from the movable member and the stationary member through an electrical path bent from an electrical path parallel to each other.
The arrangement may be such that an arc runner extending along the current supplying conductor to the stationary member is provided, the tip portion of the arc runner being exposed to the arc extinguisher plate side.
The arrangement may be such that an insulator defining an arc runner cylindrical space around the arc runner is provided.
The arrangement may be such that a commutation electrode connected to the current supplying conductor of the movable member of which tip portion reaches close to the arc extinguishing plate is disposed behind the movable member.
The arrangement may be such that the commutation electrode is provided with a slit for allowing the rotation of the movable member so that the movable contact is positioned close to the commutation electrode in the movable member open position.
The arrangement may be such that the cylindrical space of the cylindrical insulator has a configuration of expanding toward the arc extinguishing plate.
The arrangement may be such that the height of the inner wall of the cylindrical insulator on the side of the movable member rotary center is higher than the wall on the opposite side of the movable member rotary shaft in order that the movable member side opening portion of the cylindrical space defined by the cylindrical insulator faces toward the arc extinguishing plate.
The arrangement may be such that the material of the cylindrical insulator defining the cylindrical space is different between the portion surrounding the contact pair and the other remaining portion, the portion surrounding the contact pair being made of a material that easily emits a large amount of vapor by the electric arc.
The arrangement may be such that the inner wall defining the cylindrical space has a sectional shape following the rotary locus of the movable member tip.
The arrangement may be such that the portion of the stationary member positioned within the cylindrical space and around the stationary contact is covered by an insulator so that the stationary contact alone is exposed to the cylindrical space.
The arrangement may be such that, in an open end of the cylindrical space defined by the cylindrical insulator, the height of the wall of the cylindrical insulator close to the movable member rotary center is lower than the height of the wall on the side far from the movable member rotary center.
The arrangement may be such that a portion of the movable arm opposing to the stationary member and in which a current flows in opposite direction to that in the stationary member is bent to be close to the stationary member.
The arrangement may be such that the stationary conductor opposing to the movable member and in which a current flows in opposite direction to that of the movable member in the closed state is bent toward the movable member.
The arrangement may be such that a portion of the movable arm directly facing the stationary contact surface on the side of the movable member rotating center is covered with an insulator.
The arrangement may be such that two pairs of the contact pair of the movable member and the stationary member are provided and these contact pairs are electrically connected in series and separated from each other by a partition wall.
The arrangement may be such that the device is connected in the longitudinal direction to a circuit interrupter with their housings to provide a unitary structure.